Using a second iMac as a second display

I just bought a new 27" iMac, and I'm looking to get a second display for it. I was considering the cinema display, but I thought it might make more sense to get a second refurbished iMac and use it instead, since the panels are identical.

I know that the second iMac can be used in target display mode, as long as I've got a Mini DisplayPort to Mini DisplayPort cable.

Has anyone done this? When the second iMac is being used in target monitor mode, can I control it through Apple Remote Desktop and use the processor to encode videos or some other activity? Can I access the hard drive through the network?

Is there a way to make sure iMac#2 always stays in Target display mode? It would be slightly annoying to have to re-connect the cable every time I use the computer (though I suppose the command+f2 key combo isn't that annoying)

Right now the (Canadian) price for a refurb 27" iMac is 1049, and the price for a new cinema display is $1099. If this can work at all, it seems to make sense to do it.